It just depends on what you want.
If you want mad plugin capability, and stability....winamp 2.x IMHO. QCD is pretty good as well, although i've had it crash here and there.
If you want a no frills, stable, easy to use, and crash free, light proggie.....you simply can't beat foobar. Who the hell needs a grx equalizer anyway. Gimme playlists, and gimme basic controls......foobar is the best when it comes to that......I only have one request for foobar to make it top notch....gimme a draggable track position, instead of just +/- intervals. FOOBAR has never crashed on me once.
WMP 9 is ok w/ the dockable part----but I just never got used to it. Plus, like has already been said...DRM, and that means hell no.